Kitchen Gas Appliances - ground joint union needed????

Hello,
We just had propane gas piped in the house, I was told to use a ground joint union at the water heater and furnace, this is all piped in black iron pipe. So I was told to put this GJU after the appliance shut off and before the tee and above the drip leg.

Why is this used and is it needed?

thanks

Hello: appliancepresid

Yes. I agree. Install the ground joint union as instructed. Not sure why one is needed at the water heater unless it is connected to a circulation pump or is large enough to have an electric spark pilot ignition.

Any appliance connected to an electrical power source is capable of producing a tiny amount of electrical current in the piping system. Which causes electrolysis in the piping system.

Electrolysis even in very tiny amounts causes pipe corrosion to the sections in the ground. Grounding the gas line from electrical current is essential to prevent pipe corrosion from resulting.

Which is why underground lines have anodes installed on them some where in every neighborhood as it pertains to natural gas lines. Which is also the case for any underground propane lines.

Another factor is local codes and to insure the integrity and longevity of the gas suppliers under ground lines. Should your piping system be the cause of any electric current in their lines, the damage it causes and the cost of repairs can be charged back to you, in some cases.

Protect their lines and yourself, insulate as instructed and to meet all codes.

Is just a plain ordinary union, to facilitate disconnecting the appliance!! Ground Joint is only used to distinguish it from a gasketed type union!!

Unions with a brass inset in the face and a ball shaped second part are ground joint!! When they are manufactured the ball and seat are ground together with grinding compound, much like automobile valves!! Hope this explains it clearly!! Jerry